A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3738240 can be evenly divided by 1 2 3 4 5 6 8 9 10 11 12 15 16 18 20 22 24 30 32 33 36 40 44 45 48 55 59 60 64 66 72 80 88 90 96 99 110 118 120 128 132 144 160 165 176 177 180 192 198 220 236 240 264 288 295 320 330 352 354 360 384 396 440 472 480 495 528 531 576 590 640 649 660 704 708 720 792 880 885 944 960 990 1,056 1,062 1,152 1,180 1,298 1,320 1,408 1,416 1,440 1,584 1,760 1,770 1,888 1,920 1,947 1,980 2,112 2,124 2,360 2,596 2,640 2,655 2,832 2,880 3,168 3,245 3,520 3,540 3,776 3,894 3,960 4,224 4,248 4,720 5,192 5,280 5,310 5,664 5,760 5,841 6,336 6,490 7,040 7,080 7,552 7,788 7,920 8,496 9,440 9,735 10,384 10,560 10,620 11,328 11,682 12,672 12,980 14,160 15,576 15,840 16,992 18,880 19,470 20,768 21,120 21,240 22,656 23,364 25,960 28,320 29,205 31,152 31,680 33,984 37,760 38,940 41,536 42,480 46,728 51,920 56,640 58,410 62,304 63,360 67,968 77,880 83,072 84,960 93,456 103,840 113,280 116,820 124,608 155,760 169,920 186,912 207,680 233,640 249,216 311,520 339,840 373,824 415,360 467,280 623,040 747,648 934,560 1,246,080 1,869,120 and 3,738,240, with no remainder.
Since 3,738,240 cannot be divided by just 1 and 3,738,240, it is not a prime number.